1. Field
Example embodiments relate to semiconductor memory devices and methods of fabricating the semiconductor memory devices. Also, example embodiments relate to semiconductor memory devices including recess-type control gate electrodes and methods of fabricating the semiconductor memory devices including the recess-type control gate electrodes.
2. Description of Related Art
In line with the current trend of reducing the size and increasing the operating speed of semiconductor products, semiconductor memory devices used for the semiconductor products may be further integrated to attain high operating speeds. Accordingly, semiconductor memory devices including a three dimensional structure instead of a related art planar-type structure have been introduced. The semiconductor memory devices including the three dimensional structure may include recess-type control gate electrodes that extend inside a semiconductor substrate.
The semiconductor memory devices including the three-dimensional structure may have channel areas wider than semiconductor memory devices including a planar-type structure, and thus have faster operating speeds. However, in the semiconductor memory devices including the three-dimensional structure, a unit cell is operated by unit bits while occupying a large area.
Therefore, the further increase in integration of the three-dimensional semiconductor memory devices is limited. Moreover, source regions and drain regions still occupy wide areas in the semiconductor memory devices including the three dimensional structure. Particularly, the source regions and the drain regions may be alternately disposed to occupy larger areas even in “not and” (NAND) semiconductor memory devices that may be suitable for integration, which thus limits the increase in integration.